In order to form vapor deposit films of various metals in the conventional process for manufacturing electroluminescence (EL) elements and other electronic devices, a metal mask is used for forming the desired pattern on the metal films of chromium, stainless steel, and so forth.
The metal mask may be manufactured using the following methods.
(1) On a thin stainless steel sheet or other metal sheet, a resist film is formed. This resist film is exposed to form the desired mask pattern. By using this mask, the thin stainless steel sheet is etched to form a metal mask with the desired pattern.
(2) A resist film is formed on the surface of a stainless steel or other electroconductive material. The resist film is exposed to form the desired mask pattern. Thereafter, by means of an electroplating method, a metal plating layer is formed on the upper surface of the electroconductive material. The metal plating layer is then separated from the upper surface of the electroconductive material to form a metal mask with the desired pattern.
However, for the conventional methods for manufacturing metal masks, the precision of the mask during exposure and the precision of etching have a significant influence on the pattern precision of the metal mask as the final product. Consequently, in the various steps, it is necessary to control the dimensions of the pattern at a high precision. Moreover, in the conventional methods, the metal mask is formed on chromium, stainless steel, or other metals with a high linear expansion coefficient. This resulted in a problem where even a small difference in temperature in the metal material leads to a difference in the dimensional precision between the manufactured metal masks, thereby making it difficult to obtain metal masks having the same dimensional precision.
Also, the metal masks are prone to variations over time in the dimensions of the material that forms the metal mask and in the dimensions of the stainless steel as the feed material for preparing the metal mask. Thus, when many metal masks having high-precision dimensions and small variations in the dimensions are required, a problem was the difficulty in consistently manufacturing metal masks with the same dimensional precision.
For example, when multiple metal masks with the same dimensional precision in the mask pattern are to be manufactured, it is possible to form the metal masks with high precision having little variation at the beginning. However, as the manufacturing progresses over time, variations occur in the dimensions, so that the dimensional precision decreases gradually. Finally, not only does the dimensional precision degrade, but also the variations in the dimensions becomes larger. Consequently, it is difficult to obtain multiple metal masks with high precision and little variation.
The present invention takes into consideration the above-mentioned problems and is intended to provide a method for manufacturing a metal mask wherein control of the dimensions can be performed easily, and multiple high-precision metal masks can be formed with each having dimensions of the same precision.